Acaricidal combinations of neem seed extract and bifenthrin

ABSTRACT

Combinations of bifenthrin with azadirachtin-containing neem seed extracts are synergistic in controlling acarids, especially pyrethroid-resistant mites, over a wide range of azadirachtin to bifenthrin ratios.

The present invention relates to methods for controlling acarids. Inparticular, it relates to the application of combinations of bifenthrinand an extract from seeds of the African/Asian neem tree (Azadirachtaindica) to the locus where acarid control is desired. The combinationhas been found especially effective in the control ofpyrethroid-resistant mites.

Bifenthrin is a known pyrethroid insecticide. Neem seed extract, acomplex mixture including several bioactive compounds, has long beenknown to have insecticidal and insect feeding inhibition properties,generally attributed to the compound azadirachtin. Synergisticinteractions have been reported for different neem extracts with avariety of materials, including piperonyl butoxide, common vegetableoils, and several different insecticides, including pyrethrins andsynthetic pyrethroids. However, combinations of pyrethroids with neemextracts are not always synergistic. Synergism is shown by Qadri and Rao(Pesticides (Bombay), 14(3), 11, 1980), who report a combination ofpyrethrins and neem seed extract is more effective against certainhousehold and stored products pests than would be expected from theindividual contributions of the components. A brochure put out byAgriDyne Technologies Inc. suggests possible synergism between a neemseed extract and s-fenvalerate against cabbage looper. On the otherhand, Samuthiravelu and David (The Madras Agricultural Journal, 77, 294,1990) report that combinations of deltamethrin and neem seed extract areno better at controlling the spotted boll worm on cotton than isdeltamethrin alone. Other publications suggest using neem extracts incombination with pyrethrins or pyrethroids to control insects, notnecessarily for any possible synergism, but for their different modes ofaction. No report of synergism against acarids has been found.

The only report found in which bifenthrin and a neem seed extract wereused in combination is in a second brochure put out by AgriDyneTechnologies Inc. In that brochure several insecticides, both alone andin combination with Azatin™ insecticide, a neem seed extract containing3.0% azadirachtin, are tested for control of the sweetpotato whitefly.However, from the information presented it is not possible to tell ifthe combination of Azatin with bifenthrin is better than bifenthrinalone.

Neither bifenthrin nor the neem extracts, when applied alone at therates tested, control pyrethroid-resistant twospotted spider mite. Theefficacy of the apparent synergistic combination of these two knowninsecticides against this species is heretofore unknown.

Bifenthrin, which is known to be effective against a broad range offoliar-feeding pests, is described in U.S. Pat. No. 4,238,505 and hasthe following structure ##STR1##

Azadirachtin, an organic molecule belonging to a class of compoundsknown as tetranortriterpenoids, to which the insecticidal activity ofneem extract is commonly attributed, has the following structure:##STR2##

Azadirachtin is known to interfere with insect molting, reproduction,and digestion.

It has now been found that combinations of bifenthrin andazadirachtin-containing neem seed extracts are synergistic in theircontrol of pyrethroid-resistant twospotted spider mites over a widerange of ratios. Surprisingly, these combinations appear somewhatantagonistic in their control of a strain of twospotted spider mitesusceptible to pyrethroids.

Bifenthrin, azadirachtin, and the combinations were tested against bothsusceptible and pyrethroid-resistant twospotted spider mite (Tetranychusurticae). In these tests, the compounds were tested as technicalmaterials or as formulations. The technical materials were tested as 10%acetone/water solutions (v/v) containing 0.1% of the surfactantoctylphenoxypolyethoxyethanol. The formulated materials were tested aswater solutions.

Bifenthrin was tested as a technical material and as a 2 EC formulation(an emulsifiable concentrate containing 2.0 lb of technical bifenthrin(95% active ingredient) per gallon of formulation). A typical 2 ECformulation of bifenthrin consists of (weight/weight) 26.53% technicalbifenthrin, 7.51% emulsifiers, and 65.96% inert diluent and solvent.

Technical neem seed extract was a solid material containing 15.9%azadirachtin, as analyzed by HPLC. This solid was obtained from AgridyneTechnologies Inc., 417 Wakara Way, Salt Lake City, Utah 84108. Theidentities of the remaining components of this solid extract were notdetermined.

One neem seed extract formulation used in these tests was Margosan-O®,Botanical Insecticide Concentrate (Grace Sierra Crop Protection Co.,1001 Yosemite Dr., Milpitas, Calif. 95035),an ethanol extract of neemtree seeds containing about 3000 ppm (0.3% ai) of azadirach-tin andabout 20% neem oil, to which has been added polyoxyethylene sorbitanmonolaurate or octylphenoxy-polyethoxyethanol (emulsifiers), andadjusted to pH 4.0 with ammonium hydroxide.

Another neem seed extract formulation used in these tests was Azatin™Insecticide (obtained from Agridyne Technologies Inc.). This formulationcontains about 3.0% azadirachtin, 27% other neem plant compounds, and70% inert ingredients that one would find in a typical emulsifiableconcentrate formulation.

For the tests against the twospotted spider mites, a 100×15 mmpolystyrene petri dish for each of two replicates of each rate ofapplication was lined with a cotton pad. The cotton pad was moistenedwith about 10-15 mL of distilled water. Three leaf discs, each 2.5 cm indiameter, were punched from the leaves of a lima bean plant (Phaseoluslunatus) and placed bottom side up on the cotton pad in each dish. Eachdisc was infested with about 10-15 adult female mites with the aid of amicroscope and a small artist's brush. A hand-held DeVilbiss sprayer wasused to spray the discs at 5-10 psi with a test solution of theappropriate concentration until the leaf surfaces were evenly coveredwith the spray solution. The combinations of bifenthrin and azadirachtinwere sprayed as mixtures. The discs were allowed to dry for about 1-2hours. The petri dishes containing the discs were then covered withtheir lids and placed in a growth chamber, where they were maintainedfor a 72-hour exposure period at 24° C. and 50% relative humidity and alight/dark cycle of 15 hr/9 hr. Mortality counts were taken after the 72hours of exposure time. The results reported in each Table areside-by-side tests, so as to minimize the variability inherent in testson living organisms.

Table 1 shows the results of tests on pyrethroid-susceptible mites. Itis clear that there is no synergism, and in fact the two materialsappear antagonistic.

Tables 2 through 7 show a variety of tests with technical neem seedextract and the two neem extract formulations, where the concentrationis given in terms of azadirachtin content, and technical bifenthrin andformulated bifenthrin. Table 2, in which technical materials are used,shows synergism over a bifenthrin to azadirachtin ratio of 4:1 to4000:1! In Tables 3 and 4 two different concentrations of bifenthrin anda narrower range of azadirachtin concentrations were used. Synergism isshown for each combination tested. Table 4 is similar to Table 3, exceptthat formulated extract is used rather than technical. Tables 3 and 4show synergism over a range of 400:1 to 20:3. Tables 5 and 6 showsynergism over a wider range of bifenthrin concentrations with two neemextract concentrations. Table 6 repeats the concentrations of Table 5,but with each component as a formulation, with the demonstratedbifenthrin to azadirachtin synergism range 540:1 to 54:3. Table 7extends the bifenthrin/azadirachtin ratio to 3:10.

In summary, in different tests at different times, synergism has beendemonstrated for combinations of three different azadirachtin-containingneem seed extracts with technical and formulated bifenthrin over a rangeof ratios of bifenthrin to azadirachtin of 4000:1 to 3:10, with a greatnumber of intermediate ratios.

In normal use the acaricidal bifenthrin/neem seed extract combinationsof the present invention usually will not be employed free fromadmixture or dilution, but ordinarily will be used in a suitableformulated composition compatible with the method of application andcomprising an acaricidally effective amount of the combination. Thecombinations of this invention, like most pesticidal agents, may beblended with the agriculturally acceptable surface-active agents andcarriers normally employed for facilitating the dispersion of activeingredients, recognizing the accepted fact that the formulation and modeof application of an insecticide may affect the activity of thematerial. The present bifenthrin/neem seed extract combinations may beapplied, for example, as sprays, dusts, or granules to the area wherepest control is desired, the type of application varying, of course,with the pest and the environment. Thus, the combinations of thisinvention may be formulated as granules of large particle size, aspowdery dusts, as wettable powders, as emulsifiable concentrates, assolutions, and the like.

Granules may compose porous or nonporous particles, such as attapulgiteclay or sand, for example, which serve as carriers for the combinations.The granule particles are relatively large, a diameter of about 400-2500microns typically. The particles are either impregnated with thecombination from solution or coated with the combination, adhesivesometimes being employed. Granules generally contain 0.05-10%,preferably 0.5-5%, active ingredient as the acaricidally effectiveamount.

Dusts are admixtures of the combinations with finely divided solids suchas talc, attapulgite clay, kieselguhr, pyrophyllite, chalk, diatomaceousearths, calcium phosphates, calcium and magnesium carbonates, sulfur,flours, and other organic and inorganic solids which act as carriers forthe insecticide. These finely divided solids have an average particlesize of less than about 50 microns. A typical dust formulation usefulfor controlling acarids contains 1part of the synergistic combinationand 99 parts of talc.

The synergistic combinations of the present invention may be made intoliquid concentrates by dissolution or emulsification in suitable liquidsand into solid concentrates by admixture with talc, clays, and otherknown solid carriers used in the pesticide art. The concentrates arecompositions containing, as an acaricidally effective amount, about5-50% of the combination and 95-50% inert material, which includessurface-active dispersing, emulsifying, and wetting agents, but evenhigher concentrations of active ingredient may be employedexperimentally. The concentrates are diluted with water or other liquidsfor practical application as sprays, or with additional solid carrierfor use as dusts.

Useful liquid concentrates include the emulsifiable concentrates, whichare homogeneous liquid or paste compositions readily dispersed in wateror other liquid carriers. They may consist entirely of a concentrate ofa combination of the invention with a liquid or solid emulsifying agent,or they may also contain a liquid carrier such as xylene, heavy aromaticnaphthas, isophorone and other relatively non-volatile organic solvents.For application, these concentrates are dispersed in water or otherliquid carriers and normally applied as sprays to areas to be treated.

Typical surface-active wetting, dispersing, and emulsifying agents usedin pesticidal formulations include, for example, the alkyl and alkylarylsulfonates and sulfates and their sodium salts, including fatty methyltaurides; alkylaryl polyether alcohols; sulfates of higher alcohols;polyvinyl alcohols; polyethylene oxides; sulfonated animal and vegetableoils; sulfonated petroleum oils; fatty acid esters of polyhydricalcohols and the ethylene oxide addition products of such esters; andthe addition products of long-chain mercaptans and ethylene oxide. Manyother types of useful surface-active agents are available in commerce.The surface-active agent, when used, normally comprises about 1-15% byweight of the acaracidal composition.

Other useful formulations include simple solutions of the activeingredient in a solvent in which it is completely soluble at the desiredconcentrations, such as acetone or other organic solvents.

It is apparent that various modifications may be made in the formulationand application of the synergistic combinations of this inventionwithout departing from the inventive concepts herein as defined in theclaims.

                  TABLE 1                                                         ______________________________________                                        Tests on Twospotted Spider Mite (Pyrethroid-Susceptible)                                   % Mortality                                                              Rate   Single     A (1.3 ppm) + B                                     Component (ppm)    Component  Expected                                                                             Observed                                 ______________________________________                                        Bifenthrin(A)                                                                           1.3      48         --     --                                       Extract(B)                                                                              1000     92         100    91                                       Extract   100      19         67     72                                       Extract   10       15         63     38                                       Extract   1        14         62     36                                       ______________________________________                                         (A) is technical bifenthrin                                                   (B) is neem seed extract containing 15.9% azadirachtin, tested at             indicated ppm of azadirachtin                                            

                  TABLE 2                                                         ______________________________________                                        Tests on Twospotted Spider Mite (Pyrethroid-Resistant)                                     % Mortality                                                              Rate   Single     A (400 ppm) + B                                     Component (ppm)    Component  Expected                                                                             Observed                                 ______________________________________                                        Bifenthrin(A)                                                                           400      52         --     --                                       Extract(B)                                                                              1000     65         100    100                                      Extract   100      20         72     91                                       Extract   10       17         69     90                                       Extract   1        18         70     90                                       Extract   0.1      10         62     92                                       ______________________________________                                         (A) is technical bifenthrin                                                   (B) is neem seed extract containing 15.9% azadirachtin, tested at             indicated ppm of azadirachtin                                            

                                      TABLE 3                                     __________________________________________________________________________    Tests on Twospotted Spider Mite (Pyrethroid-Resistant)                                   % Mortality                                                               Rate                                                                              Single                                                                              A (400 ppm) + B                                                                         A (200 ppm) + B                                    Component                                                                            (ppm)                                                                             Component                                                                           Expected                                                                           Observed                                                                           Expected                                                                           Observed                                      __________________________________________________________________________    Bifenthrin(A)                                                                        400 52    --   --   --   --                                            Bifenthrin                                                                           200 23    --   --   --   --                                            Extract(B)                                                                           30  5     57   96   28   91                                            Extract                                                                              10  6     58   93   29   82                                            Extract                                                                              3   1     53   95   24   83                                            Extract                                                                              1   0     52   86   23   63                                            __________________________________________________________________________     (A) is technical bifenthfin                                                   (B) is neem seed extract containing 15.9% azadirachtin, tested at             indicated ppm of azadirachtin                                            

                                      TABLE 4                                     __________________________________________________________________________    Tests on Twospotted Spider Mite (Pyrethroid-Resistant)                                   % Mortality                                                               Rate                                                                              Single                                                                              A (400 ppm) + C                                                                         A (200 ppm) + C                                    Component                                                                            (ppm)                                                                             Component                                                                           Expected                                                                           Observed                                                                           Expected                                                                           Observed                                      __________________________________________________________________________    Bifenthrin(A)                                                                        400 52    --   --   --   --                                            Bifenthfin                                                                           200 23    --   --   --   --                                            Extract(C)                                                                           30  51    100  100  74   98                                            Extract                                                                              10  2     49   95   25   96                                            Extract                                                                              3   6     53   90   29   86                                            Extract                                                                              1   6     53   88   29   69                                            __________________________________________________________________________     (A) is technical bifenthrin                                                   (C) MargosanO ® insecticide is a neem seed extract containing 0.3%        azadirachtin, tested at indicated ppm of azadirachtin                    

                                      TABLE 5                                     __________________________________________________________________________    Tests on Twospotted Spider Mite (Pyrethroid-Resistant)                                   % Mortality                                                               Rate                                                                              Single                                                                              B (10 ppm) + A                                                                          B (1 ppm) + A                                      Component                                                                            (ppm)                                                                             Component                                                                           Expected                                                                           Observed                                                                           Expected                                                                           Observed                                      __________________________________________________________________________    Extract(B)                                                                           10  0     --   --   --   --                                            Extract                                                                              1   1     --   --   --   --                                            Bifenthrin(A)                                                                        1000                                                                              96    96   98   97   94                                                   540 69    69   91   70   93                                                   300 58    58   98   59   98                                                   100 52    52   84   53   89                                                   30  8     8    82   9    78                                            __________________________________________________________________________     (A) is technical bifenthrin                                                   (B) is neem seed extract containing 15.9% azadirachtin, tested at             indicated ppm of azadirachtin                                            

                                      TABLE 6                                     __________________________________________________________________________    Tests on Twospotted Spider Mite (Pyrethroid-Resistant)                                   % Mortality                                                               Rate                                                                              Single                                                                              C (10 ppm) + D                                                                          C (1 ppm) + D                                      Component                                                                            (ppm)                                                                             Component                                                                           Expected                                                                           Observed                                                                           Expected                                                                           Observed                                      __________________________________________________________________________    Extract(C)                                                                           10  85    --   --   --   --                                            Extract                                                                              1   0     --   --   --   --                                            Bifenthfin(D)                                                                        1000                                                                              100   100  100  100  100                                                  540 74    100  98   74   98                                                   300 56    100  95   56   96                                                   100 49    100  86   49   86                                                   30  0     85   97   0    65                                            __________________________________________________________________________     (C) MargosanO ® insecticide is a neem seed extract containing 0.3%        azadirachtin, tested at indicated ppm of azadirachtin                         (D) an emulsifiable concentrate containing 2.0 pounds of technical            bifenthrin per gallon of formulation, tested at indicated ppm bifenthrin.

                                      TABLE 7                                     __________________________________________________________________________    Tests on Twospotted Spider Mite (Pyrethroid-Resistant)                        __________________________________________________________________________           Rate                                                                              Single                                                                              Expected                                                                           Observed                                                                           Expected                                                                           Observed                                                                           Expected                                                                           Observed                            Component                                                                            (ppm)                                                                             Component                                                                           A (30 ppm) + B                                                                          A (10 ppm) + B                                                                          A (3 ppm) + B                            __________________________________________________________________________    Extract(B)                                                                           10  7     10   92   8    98   7    89                                  Extract                                                                              1   6     9    89   7    82   6    67                                  Bifenthrin(A)                                                                        30  3                                                                  Bifenthrin                                                                           10  1                                                                  Bifenthrin                                                                           3   0                                                                  __________________________________________________________________________           Rate Single D (30 ppm) +                                                                            D (10 ppm) +                                                                            D (3 ppm) +                            Component                                                                            (ppm)                                                                              Component                                                                            Extract   Extract   Extract                                __________________________________________________________________________    Extract(C)                                                                           10   58     62   98   61   98   65   85                                Extract(C)                                                                           1    0      4    91   3    93   7    79                                Extract(E)                                                                           10   16     20   95   19   92   23   85                                Extract(E)                                                                           1    5      9    91   8    91   12   79                                Bifenthrin(D)                                                                        30   4                                                                 Bifenthrin                                                                           10   3                                                                 Bifenthrin                                                                           3    7                                                                 __________________________________________________________________________     (A) is technical bifenthfin                                                   (B) is neem seed extract containing 15.9% azadirachtin, tested at             indicated ppm of azadirachtin                                                 (C) MargosanO ® insecticide is a neem seed extract containing 0.3%        azadirachtin, tested at indicated ppm of azadirachtin                         (D) an emulsifiable concentrate containing 2.0 pounds of technical            bifenthfin per gallon of formulation, tested at indicated ppm bifenthrin      (E) Azatin ™ insecticide is a neem seed extract containing 3.0             azadirachtin, tested at indicated ppm azadirachtin.                      

We claim:
 1. A method of controlling pyrethroid resistant mites which comprises applying to the site where control is desired an acaricidally effective amount of an azadirachtin-containing neem seed extract and bifenthrin, the ratio of azadirachtin to bifenthrin being in the range of 10 to 3 to 1 to
 4000. 2. A method of claim 1 in which the mites are Tetranychus species.
 3. The method of claim 2 in which the mites are twospotted spider mites.
 4. A method of controlling pyrethroid resistant mites which comprises applying to the site where control is desired a composition containing an acaricidally effective amount of an azadirachtin-containing neem seed extract and bifenthrin, the ratio of azadirachtin to bifenthrin being in the range of 10 to 3 to 1 to
 1000. 5. A method of claim 4 in which the mites are Tetranychus species.
 6. The method of claim 5 in which the mites are twospotted spider mites. 